1. Field of the Invention
The present invention relates to a method for connecting a surgical instrument to a medical console and, more particularly, to an electrical adapter for connecting a new surgical instrument having a brushless direct current (D.C.) motor to an existing medical console having a two-wire controller designed for connection to brushes in a commutated D.C. motor.
2. Discussion of the Related Art
Brushless D.C. motors are becoming commonplace in many medical applications, especially ear, nose and throat (ENT) surgery, due to advantages such as increased reliability, increased life expectancy and reduced radio frequency emissions or interference (RFI). Brushless motors do not include parts associated with mechanical commutation (e.g., brushes) and so arcing is eliminated. One difficulty encountered in using brushless D.C. motors in surgical instruments, such as shavers, is that many of the medical consoles presently in use in hospitals and other medical facilities have controller circuits adapted for use with two-wire, commutated D.C. motors, and replacement of existing medical consoles would require an unacceptable expense. Medical consoles with two-wire controllers apply voltage in one of two possible polarities. For a first polarity, the commutated D.C. motor spins clockwise (CW) and with the opposite polarity voltage applied, the motor spins counter clockwise (CCW).
Brushless D.C. motors do not have brushes to commutate the motor, and a motor controller for use with brushless D.C. motors must sense the position of the motor rotor and commutate (i.e., control the direction and position) the motor electronically. Accordingly, the brushless motor controllers of the prior art are incompatible with and more complex than the two-wire motor controllers used in the existing medical consoles.
In the past, the high RFI emissions associated with arcing brushes in commutated D.C. motors were of little concern to surgical instrument designers or users. In the modern ENT surgical facility, however, computers and a wide variety of wireless communications devices are employed and can be impaired by emissions from any device having poor RFI performance. As an example, new ENT stereotactic surgical imaging systems incorporate sensors and computers with little tolerance for RF emissions, and use of a surgical instrument with a commutated D.C. motor is more likely to compromise imaging system performance.